Spot on.The thing to do in such circumstances is always either
- to pay the fare and keep the ticket
- not travel but record details of route, time, place and bus fleet number
and the always write and complain to the operator.
Only by so doing will they become aware of an issue and have an opportunity to take steps. If it's specific to a few drivers (which is why you need the data) then they can be trained; if its generic then the company needs to do something bigger. But they need to be told, with specifics, that their staff are getting it wrong.
Stagecoach Manchester's inability to get their drivers to accept PlusBus without fail was the reason I gave up on getting the bus to Salford, and now pay extra for the tram. The tipping point was when two drivers in as many hours started off with 'not valid mate'. I've only ever had one problem with First and that was sorted fairly quickly.
On one occasion, the PlusBus sticker was on the bus window and I was still told 'that's just for the train' by one hopeless driver. You can't win sometimes.